Stylus and method of making same



Nov. 26, 1957 A. w. PLOEGSMA 2,814,495

STYLUS AND METHOD OF MAKING SAME Filed June 16, 1954 INVENTOR. v ANTONIE WOBBE PLOEGSMA AGENT United States Patent STYLUS AND METHOD OF MAKING SAME Antonie Wobbe Ploegsma, Eindhoven, Netherlands, as-

signor, by mcsne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application June 16, 1954, Serial No. 437,236

Claims priority, application Netherlands June 16, 1953 4 Claims. (Cl. 274--38) It has for a long time been attempted to replace the well-known steel or sapphire gramophone needles by needles made from a material whereof the hardness exceeds that of said materials. Of course, this is advantageous in view of the resistance to wear of said material and, moreover, it has been found in practice that the wearing out of gramophone records is mainly due to the grinding effect of the abraded particles of the needle on the groove. Hence, the life both of the needle and of the record is longer as the abrasion of the needle is lesser.

For gramophone needles it is known to employ diamond splinters, such as they are found in nature or ensue from cutting diamonds. This has several disadvantages since it is Well-nigh impossible to test all the splinters for purity. Moreover, the mounting in a holder entails difficulties due to the irregular shape of the splinters, so that said operation is to be carried out by skilled craftsmen. It is known that much rejected material occurs in grinding the splinters, while a further part perishes during the mounting operation.

Surprisingly enough to the man skilled in the art, it has now been found that, in accordance with the invention, cylindrical, more especially stylus-shaped articles of a maximum diameter of approximately 1 mm. and made from a material having a Vickers hardness in excess of 1900, can be manufactured by bringing the end of a. thin-walled tube, whereof the inside diameter corresponds to the desired diameter of the cylindrical article and which is rotated and intermittently brought even deeper into contact with a piece of said material, the active end of the tube being provided with finely divided material having the same or a greater hardness than that of the material of which the article consists and the operation being continued until the piece has been pierced from front to back. In accordance with the invention it is thus feasible to obtain circular, stylus-shaped articles adapted to be easily mounted in mass-production. Said piece, which is comparatively large relatively to the articles to be made may previously be tested for the presence of inclusions, air bubbles or the like.

In one embodiment of the invention, the abrasive provided on the end of the tube preferably consists of diamond powder having a grain-size of approximately to 25 microns.

The method according to the invention is particularly suitable for making gramophone needles. The blank may, for example, be a diamond which, upon examination, proves to be perfectly free from faults or is possessed of faultless areas. In the carrying out of the invention a number of cylindrical articles are made from such a diamond and subsequently the remainder of the diamond, which is unsuitable for making further articles, may be disintegrated to diamond powder. It has proved feasible to make diamond needles for use in pick-ups, which needles have a diameter of 0.35 mm. and a tolerance of 20 microns or less. The needle can easily be provided with a suitable point and its mounting does not entail difiiculties.

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Cylindrical articles made in accordance with the invention are also particularly suitable for use as a cutting element of cutting tools, for example a turning tool, a planing tool, a milling cutter and suchlike tools.

In one embodiment of the invention the material from which the stylus-shaped article is made may advantageously be a diamond die which as such is unfit for further use because its bore is Worn out above a given value in connection with the size of the diamond, or which die exhibits a crack. Such a diamond is perfectly free from inclusions but hitherto it could only be further used for working up into diamond powder. The method according to the invention permits of an additional number of needles to be made from such a die and the remainder to be worked up into diamond powder.

In order that the invention may be readily carried into efiect, it will now be described with reference to the accompanying drawing, given by way of example, in which:

Fig. 1 illustrates the manner of making diamond gramophone needles,

Fig. 2 is a plan view of a turning tool comprising a diamond stylus as a cutting element,

Fig. 3 is a front view of said turning tool,

Fig. 4 is a view of a phonograph stylus, and

Fig. 5 is an elevational view of a tip blank produced by the method shown in Fig. 1.

In Fig. l, a diamond is denoted by 1. To a thinwalled metal tube 2 both a rotatory and a reciprocating movement are imparted as indicated. To the grinding end 3 of the tube diamond powder is supplied, for example in the form of a dispersion of diamond powder in a liquid, for example oil. The tube may be, for example, have an inside diameter of 0.35 mm., an outside diameter of 0.5 mm. and may be made from rustless so-called V2a steel. The diamond may advantageously be a worn out die.

With reference to Fig. 2, the reference numeral 4 designates the body of a turning tool whose cutting point 5 is a diamond needle.

Fig. 3, which is a front view on a greatly enlarged scale of Fig. 2, illustrates that the diamond needle has been provided, by grinding, with a fiat 6 so that the needle is more rigidly maintained in position. In accordance with U. S. patent application, Serial No. 301,664, now abandoned, the material of the body of the turning iron is preferably bell metal with a content of copper and 20% tin.

Alternatively, other hard materials may be employed for manufacturing cylindrical articles in accordance with the invention. Preferably, the materials chosen will be as homogeneous as possible and, if made synthetically, the particles may, for example, be sintered to compactness at a high temperature and pressure.

The well-known sapphire needles may also be made in accordance with the invention, thus greatly reducing the loss of material as compared with the hitherto employed methods.

Referring now to Figure 5 wherein is shown a diamond stylus 7 after it has been drilled out of a diamond blank 1 by means of metal tube 2. The stylus is of a circular form and has circumferential ridges 8 thereon extending in a direction perpendicular to the longitudinal axis of stylus 7. The tip 9 of the stylus is then ground to form a. generally conical shape as seen in Fig. 4. Fig. 4 moreover illustrates the finished stylus 7 secured in a stylus holder 10.

What is claimed is:

1. A method of manufacturing an article comprising a base portion and a cylindrically shaped diamond member having a body portion secured in said base portion and having a surface-engaging end-portion extending from said base portion, said diamond member having a given diameter not exceeding a maximum value of the order of one millimeter, said method comprising the steps of providing a diamond blank having a surface area and a depth dimension greater than said given diameter, engaging a selected portionof said diamond blank with the end of a thin-walled tubular metal tool having an inside diameter substantially equal to the said given diameter of said diamond member, providing the diamond blank engaging end of said tool with an abrasive constituted of finely divided material having a hardness of at least as great as the hardess of said diamond blank, rotating said tool around the axis thereof and intermittently increasing the contact force between the end of said tool and said diamond blank while rotating said tool thereby to form from said blanka cylindrical diamond member having said given diameter, providing a point at one end of the so formed diamond member, and mounting said so formed diamond member into the said base portion with one end portion thereof extending from said base portion.

2. A method of manufacturing an article comprising a base portion and a cylindrically shaped diamond member having a body portion secured in said base portion and having a surface-engaging end-portion extending from said base portion, said diamond member having a given diameter not exceeding a maximum value of the order of one millimeter, said method comprising the steps of providing a diamond blank having surface area and depth dimensions greater than said given diameter, engaging a selected portion of said diamond blank with the end of a thin-walled tubular metal tool having an inside diameter substantially equal to the said given diameter of said diamond member, providing the diamond blank engaging end of said tool with an abrasive constituted of finely divided diamond particles having a size of the order of 10 to 25 microns, rotating said tool around the axis thereof and intermittently increasing the contact force between the end of said tool and said diamond blank while rotating said tool thereby to pierce said blank from front to back and form from said blank a cylindrical diamond member having said given diameter, providing a point at one end of the so formed diamond member, and mounting said so formed diamond member into the said base portion.

3. A phonograph stylus assembly comprising a stylus holder, and a diamond stylus of circular cross-section having a body portion mounted in said holder and provided with a record engaging conical end portion, said diamond stylus body portion having a plurality of ridges thereon extending in a direction substantially transverse to the longitudinal axis of said diamond stylus to thereby facilitate the mounting of said stylus body portion in said holder, and said diamond stylus having a given diameter not exceeding one millimeter.

4. A phonograph stylus assembly comprising a stylus holder, and a diamond stylus of circular cross-section having a body portion mounted in said holder and provided with a record engaging conical end portion, said diamond stylus body portion having a plurality of circumferential ridges thereon extending in a direction substantially transverse to the longitudinal axis of said diamond stylus to thereby facilitate the mounting of said stylus body portion in said holder, and said diamond stylus having a diameter of approximately 0.35 mm.

References Cited in the file of this patent UNITED STATES PATENTS 306,477 Fuller Oct. 14, 1884 922,649 Williams May 25, 1909 1,271,224 Rintelman July 2, 1918 1,988,538 Brown Jan. 22, 1935 2,127,998 Jearam Aug. 23, 1938 2,557,350 Hutter June 19, 1951 2,569,854 Hatcher Oct. 2, 1951 2,614,848 Kidd -2 Oct. 21, 1952 2,665,526 Pelton Jan. 12, 1954 

